I can get poison ivy by walking by it. Old country Dr. Told me many years ago to use lye soap after exposure to the ivy. I'm still using it. I'll find it at craft shows etc and stock up.
It may just be an old husbands tale, but it's worked fo me anyway.
Oh don't discount the rememdies. My grand mother helped me with my in grown toe nails. She said cut a vee right in the middle of my toe and you won't get them. I did and have been and no more in grown toes. Old country Dr's and Grandma's have all the good advice.